The goal of the data collection core will be to support the program by developing, testing, implementing, and monitoring all data collection activities, and by overseeing the identification and recruitment of all study subjects for all the program researchers. By centralizing these field responsibilities in the data collection core, we will avoid duplication of effort, achieve synergy of methods and significant gains in efficiency across projects, and enhance the validity of the data collected. Specifically, the data collection core, in close collaboration with the project investigators, will undertake the implementation of the gamut of all hospital- and outpatient-based activities, including: 1) working with the biostatistics and data management core in the design and pretesting of data collection instruments, 2) development of training manuals for study staff, including both general materials on field operations and material targeted to the program's instruments, 3) development and implementation of systems for subject ascertainment, 4) implementing and monitoring of sampling procedures, 5) development and testing of procedures for maximizing participation rates, 6) hiring field personnel, 7) training field personnel, 8) supervising field personnel, 9) recruiting study subjects, 10) administering interviews, 11) performing medical records reviews and abstraction, 12) collecting hospital administration data, e.g., on-call schedules, shifts, patient/M.D. ratios, intern-resident combinations, 13) monitoring of procedures for selecting potential subjects, 14) analyses related to the quantification of nonparticipation, and 15) formal quality control checks of data collection activities and the collected data. Working closely with the biostatistics and data management core and the project investigators, the data collection core investigators will initially ensure that both newly designed and standard instruments used to collect data are appropriate for the aims and analysis plans of each project and are coded and stored in a manner that facilitates careful monitoring and eventual analysis. Thereafter, the data collection core will be responsible for collecting all the data for the program. Throughout the data collection period, the core investigators will participate in data monitoring and quality control activities. Through regular meetings and e-mail communication, the data collection core will work in close and constant collaboration with the administrative core and the biostatistics and database management core, providing complementary services to ensure that all the program investigators achieve their goals in the most valid and efficient way possible. In this way, we will ensure that the services provided by the data collection core correspond fully to the projects' requirements.